Why Middle-Aged Bald Men Grow Hair on Their Backs and Shoulders

There's a scientific reason men who have less hair on their scalps have more on their bodies, but that doesn't make it any less unfortunate.

If the hair on your head and the hair on your back seem to be advancing on each other like warring armies, you might find it comforting to know that you’re not alone. You’re likely middle-aged and in need of some grooming products, but you’re also just one of the many balding men with an increasing excess of body hair. This phenomenon is triggered by the hormone dihydrotestosterone, or DHT, a derivative of testosterone that causes hair follicles on the scalp to shrink and die but does not affect hair follicles on the neck or back.

“This is why even the baldest men are never total bald,” dermatologist Susan Bard explains. “DHT is a much more potent androgen than testosterone and is responsible for many secondary male characteristics like dark terminal hairs on the face and body. DHT acts on the scalp follicles with the opposite effect.”

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Because roughly 10 percent of the body’s testosterone is converted into DHT by an enzyme called 5-alpha reductase, men with high testosterone are more prone to baldness and, for the same reason, proliferating body hair. The more T a guy has, the more DHT a guy he’s likely to have. And because of the nature of the follicles, men are more likely to end up with a “power donut” than with a totally hairless pate.

For most hairy men suffering from this condition (or enjoying it, no judgment), hormonally-driven body hair doesn’t just show up when guys go bald. It tends to arrive when boys hit puberty. And as men’s hair follicles are exposed to more hormones over time, they grow more rather than less sensitive. DHT becomes, in essence, a more effective fertilizer. This phenomenon explains why older men tend to have long and unruly ear, nose, and neck hairs.

All that said, baldness is still ultimately determined by DNA, not T. If men are genetically predisposed to growing weak follicles, they’ll likely go bald. If they are not genetically predisposed to growing weak follicles they can have relatively high levels of testosterone and full heads of hair. For the others, there are ways to intercede. Messing with DHT levels can cause erectile dysfunction and other problems, but men can use cosmetic interventions like Rogaine, laser treatment, shaving, waxing, and in extreme cases hair transplants to cover their nakedness.

It’s worth noting that men doing this because of high DHT should care more about their elevated prostate cancer risk.